The present invention relates to a novel polypropylene-based calendered or injection-molded article, and more particularly, to a novel polypropylene-based calendered or injection-molded article with little tackiness which is excellent in flexibility and transparency and molded at low temperatures.
Conventionally, calendered articles have been produced by rolling a soft resin between two or more rolls to form film-like shaped or sheet-like shaped articles having a definite thickness (also called as xe2x80x9ccalendering methodxe2x80x9d), and vinyl chloride resins have been extensively used as the soft resin. It is known that the vinyl chloride resin generates harmful substances upon burning. For this reason, it has been strongly required to develop a calendered or injection-molded article made of a substitute resin. Japanese Patent Application Laid-Open No. 5-202237 discloses a calendered article that is produced by using, as the substitute resin, a specific xcex1-olefin-polyene copolymer and an olefin polymer. However, the calendered article is poor in flexibility because a stereoregularity is as high as 98 mol %. Polypropylene is proposed as a candidate for the substitute resin. However, polypropylene is ill-balanced between flexibility and tackiness, thereby rendering it practically unusable. Recently, there has been proposed olefin polymers produced in the presence of a metallocene catalyst. Examples of such olefin polymers include a copolymer produced from ethylene and xcex1-olefin in the presence of a metallocene catalyst. However, the copolymer has a problem of increasing the tacky component when softened. Further, the copolymer is poor in transparency and surface properties, and therefore, unsuitable as a raw material of calendered articles or injection-molded articles.
An object of the present invention is to provide a polypropylene-based calendered or injection-molded article with little tackiness which is excellent in flexibility and transparency and molded at low temperatures.
As a result of extensive research, the inventors have found that the above object is achieved by a polypropylene-based calendered or injection-molded article having a tensile modulus within a specific range, and exhibiting, when measured by a differential scanning calorimeter, no melting point or a melting point which satisfies a specific relationship with the tensile modulus. The present invention has been accomplished based on this finding.
Thus, the present invention provides a polypropylene-based shaped article selected from the group consisting of calendered articles and injection-molded articles satisfying the following requirements of:
(1) having a tensile modulus TM of 5 MPa or higher; and
(2) having, when measured by a differential scanning calorimeter (DSC), no melting point or a melting point Tm (xc2x0 C.) satisfying the following formula:
TMxe2x89xa75xc3x97Tmxe2x88x92450.
As a polymer for constituting the calendered and injection-molded articles, there may be preferably used a propylene polymer [A] satisfying the following requirements of:
(1) having a component soluble in a 25xc2x0 C. hexane in a content H25 of 0 to 80% by weight;
(2) having, when measured by a differential scanning calorimeter (DSC), no melting point or a melting point Tm (xc2x0 C.) satisfying the following formula:
xcex94Hxe2x89xa76xc3x97(Tmxe2x88x92140)
wherein xcex94H is a melting endotherm (J/g); and
(3) having an intrinsic viscosity [xcex7] of 1 to 3 dl/g as measured at 135xc2x0 C. in tetralin.
The above propylene polymer [A] is preferably a propylene homopolymer [A-1] having:
(1) a meso pentad fraction [mmmm] of from 20 to 80 mol %; and
(2) a racemic pentad fraction [rrrr] satisfying, together with 1xe2x88x92[mmmm], the following formula:
[rrrr]/(1xe2x88x92[mmmm])xe2x89xa60.1.
The propylene polymer [A] is produced by polymerizing propylene, or polymerizing propylene with ethylene and/or C4-C20 xcex1-olefin, in the presence of a polymerization catalyst comprising:
(A) a transition metal compound represented by the following general formula (I): 
wherein A1, A2, E1, E2, M, X, Y, q and r are as defined hereinafter; and
(B) at least one component selected from the group consisting of a compound (B-1) capable of forming an ionic complex by reacting with the transition metal compound (A) or a derivative thereof, and an aluminoxane (B-2).